Abstract:
This study aims to compare the hydrogen evolution efficiency of photocatalysts based on titanate, tantalate, and niobium perovskite as well as some other oxides in 20% aqueous solution of various sacrificial agent. The solid-state reaction (SSR) method was used to prepare perovskites while nanopowder TiO2, Ta2O5 and Nb2O5 were used directly as purchased. 1 wt.% Pt cocatalyst was loaded on the samples by the incipient-to-wetness impregnation method; 0.2 wt.% Au, 1 wt.% Cu and 0.2 wt.% Au-0.8 wt.% Cu cocatalysts were also tested by loading them over TiO2 via deposition precipitation with urea (DPU) and sequential-DPU (S-DPU) methods. The hydrogen production rate on Pt/SrTiO3 under UV-VIS irradiation was much higher in D(+)-glucose monohydrate (GLU) (136.2 μmol/h.gcat), methanol (MeOH) (107.2 μmol/h.gcat), and ethylene glycol (EG) (112.5 μmol/h.gcat) solutions but it decreased after a maximum. However, the hydrogen generation rate in formic acid (FA) (54.8 μmol/h.gcat) and glycerol (GLY) (14.6 μmol/h.gcat) solutions were more stable. Pt/TiO2 was also tested in GLY solution, and the hydrogen production rate was found as 1146 μmol/h.gcat indicating a better potential than SrTiO3. 0.2 wt.% Au/TiO2 catalyst also produced 1085.1 μmol/h.gcat hydrogen even though Au loading is five times lower than Pt; furthermore, this catalyst also resulted in 201.4 μmol/h.gcat hydrogen, which is still significant and much higher than Pt under visible light irradiation. The distribution and size of shiny spherical gold particles around 40-50 nm size on TiO2 was observed by the scanning electron microscope (SEM) while the band gap energies were determined around 2.97 eV, which is quite close to TiO2, using UV-VIS spectroscopy by Kubelka-Munk method. X-ray diffraction (XRD) showed that mainly anatase phase exists in nanopowder TiO2 while SrTiO3 was mainly in the cubic crystal phase.
